1. Field of the Invention
The present invention relates to liquid crystal display (LCD) devices. More particularly, the present invention relates to a circuit and a method for sensing an open-circuit lamp of a backlight unit, and a display device with a circuit for sensing an open-circuit lamp of a backlight unit.
2. Discussion of the Related Art
Cathode ray tube (CRT) devices have been widely used as display devices such as televisions or monitors. However, the CRT devices have the drawbacks of heavy weight and big size.
To substitute the CRT devices, liquid crystal display (LCD) devices have been researched and developed. The LCD devices are advantageously light-weight, dimensionally compact, and have low power consumption during operation. Recently, the LCD devices have been widely used as display devices such as monitors for desktop computers, outdoor monitors of more than 30 inches, and hang-on-the-wall televisions as well as monitors for laptop computers.
Generally, LCD devices display images by controlling transmittance of external light source. Thus, the LCD devices need an external light source such as backlight units.
Backlight units are classified into an edge type and a direct type according to the position of a light source with respect to a display panel. In direct-type backlight units, a light source is disposed directly under a display panel. Since the direct-type backlight units can provide high luminance, the direct-type backlight units are widely used for large LCD devices of more than 30 inches.
A direct-type backlight unit uses a plurality of lamps as a light source. The lamp may include a cold cathode fluorescent lamp (CCFL) or an external electrode fluorescent lamp (EEFL). However, if one lamp is open-circuit, a higher voltage will be applied to the other lamps. Accordingly, this may decrease the lifespan of the lamps or affect the operation of the lamps.
To solve this problem, a circuit for sensing an open-circuit lamp may be added to an inverter. However, since the related art circuit shuts down the power only when a plurality of lamps are open-circuit, the problems of stability of the device still exist.